I created a branch from the master. Made four commits to the branch. After the third commit I created a merge request. Till the third commit, Gitlab never complained about merge conflict. On the fourth commit, it suddenly complained about merge conflict. There have been no changes in the master.
$ git branch
master
* mylocalbranch
$ git rebase master
Current branch mylocalbranch is up to date.
$ git merge master
Already up to date.
$ git mergetool
No files need merging
My merge request is fully approved. I have write access to the repository. The Merge button is greyed out. I am not sure how do I resolve the conflicts that Gitlab is complaining about. Not sure how do I get my code to master.

